The prior art has reported fabrication and testing of multiple laser devices comprising a laser having emitter characteristics and another laser having saturable absorber characteristics. Such a combination, when optically coupled and placed in a resonant cavity, is capable of Q-switching action in which it produces short optical pulses of relatively high repetition rate. For instance, optical pulses having a duration of a fraction of a nanosecond, at a repetition frequency reaching several gigacycles, have been reported. Such devices may well have substantial utility in optical communications systems for providing what corresponds to a "carrier" upon which information can be transmitted by selectively deleting certain of the optical pulses.
Solid state devices of this sort have been disclosed by Kosonocky, U.S. Pat. No. 3,270,291 and Fowler, U.S. Pat. NO. 3,303,431.
One disadvantage to the device disclosed in the above referenced prior art is that the emitter laser and saturable absorber laser were separated and, therefore, the combination exhibited losses in coupling light from one to the other section. Lasher, however, in U.S. Pat. NO. 3,427,563 as well as Basov et al. in "Investigations of GaAs Laser Radiation Pulsations" appearing in soviet Physics-- Semi-conductors, Vol. 1, No. 10, April 1968 (beginning at page 1305), disclose a combination of the type described which is formed from an integral monocrystalline semiconductor. Since the emitter and absorber sections were different regions in a single crystal, the different characteristics of these regions were obtained by pumping them with current at different levels. To prevent pumping current intended for the emitter section from leaking to the saturable absorber section, two different contacts were employed, one overlaying the emitter section and the other overlaying the saturable absorber section. In addition, a slot was cut into the semi-conductive body to act as an insulator. In practice the slot is difficult to cut properly, for it must be cut deep enough to inhibit conduction between the two regions, but at the same time not so deep as to interfere with optical properties of the device. Although the device has an active lasing region to which the optical signal is confined, it is not sufficient to stop the slot short of the active region for the characteristics of the active region depend upon, for instance, the index of refraction of the adjacent regions. If the slot extends up to the active region light can leak out through the slot. On the other hand, if the slot is stopped far enough short of the active region to prevent light leakage, conductive leakage is possible.
Furthermore, the requirment of the plurality of contacts on the body, as in Lasher, is also not desirable, although it is feasible to produce such a device. On the other hand, it would make fabrication of the device easier if only single contact were required to transmit the pumping current from the pumping source to the laser device.
It is therefore one object of the present invention to provide an integral laser capable of Q-switching which does not require slotting or cutting of the body to insulate an emitter section from an absorber section. It is another object of the present invention to provide a Q-switching solid state laser having emitter and absorber sections in which the selections are insulated from each other. It is still another object of the present invention to provide such a device capable of controllable and repetitive Q-switching. It is still another object of the present invention to provide a device of the foregoing nature which admits of relatively simpler manufacture than that found in the prior art